{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-2391","assignerOrgId":"7ffcee3d-2c14-4c3e-b844-86c6a321a158","state":"PUBLISHED","assignerShortName":"harborist","dateReserved":"2026-02-12T03:52:09.332Z","datePublished":"2026-02-12T04:39:42.914Z","dateUpdated":"2026-02-12T17:32:05.953Z"},"containers":{"cna":{"affected":[{"collectionURL":"https://npmjs.com/qs","defaultStatus":"unaffected","packageName":"qs","repo":"https://github.com/ljharb/qs","versions":[{"lessThanOrEqual":"6.14.1","status":"affected","version":"6.7.0","versionType":"semver"}]}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"### Summary
The `arrayLimit` option in qs does not enforce limits for comma-separated values when `comma: true` is enabled, allowing attackers to cause denial-of-service via memory exhaustion. This is a bypass of the array limit enforcement, similar to the bracket notation bypass addressed in GHSA-6rw7-vpxm-498p (CVE-2025-15284).
### Details
When the `comma` option is set to `true` (not the default, but configurable in applications), qs allows parsing comma-separated strings as arrays (e.g., `?param=a,b,c` becomes `['a', 'b', 'c']`). However, the limit check for `arrayLimit` (default: 20) and the optional throwOnLimitExceeded occur after the comma-handling logic in `parseArrayValue`, enabling a bypass. This permits creation of arbitrarily large arrays from a single parameter, leading to excessive memory allocation.
**Vulnerable code** (lib/parse.js: lines ~40-50):
```js
if (val && typeof val === 'string' && options.comma && val.indexOf(',') > -1) {
return val.split(',');
}
if (options.throwOnLimitExceeded && currentArrayLength >= options.arrayLimit) {
throw new RangeError('Array limit exceeded. Only ' + options.arrayLimit + ' element' + (options.arrayLimit === 1 ? '' : 's') + ' allowed in an array.');
}
return val;
```
The `split(',')` returns the array immediately, skipping the subsequent limit check. Downstream merging via `utils.combine` does not prevent allocation, even if it marks overflows for sparse arrays.This discrepancy allows attackers to send a single parameter with millions of commas (e.g., `?param=,,,,,,,,...`), allocating massive arrays in memory without triggering limits. It bypasses the intent of `arrayLimit`, which is enforced correctly for indexed (`a[0]=`) and bracket (`a[]=`) notations (the latter fixed in v6.14.1 per GHSA-6rw7-vpxm-498p).
### PoC
**Test 1 - Basic bypass:**
```
npm install qs
```
```js
const qs = require('qs');
const payload = 'a=' + ','.repeat(25); // 26 elements after split (bypasses arrayLimit: 5)
const options = { comma: true, arrayLimit: 5, throwOnLimitExceeded: true };
try {
const result = qs.parse(payload, options);
console.log(result.a.length); // Outputs: 26 (bypass successful)
} catch (e) {
console.log('Limit enforced:', e.message); // Not thrown
}
```
**Configuration:**
- `comma: true`
- `arrayLimit: 5`
- `throwOnLimitExceeded: true`
Expected: Throws \"Array limit exceeded\" error.
Actual: Parses successfully, creating an array of length 26.
### Impact
Denial of Service (DoS) via memory exhaustion.
"}],"value":"### Summary\nThe `arrayLimit` option in qs does not enforce limits for comma-separated values when `comma: true` is enabled, allowing attackers to cause denial-of-service via memory exhaustion. This is a bypass of the array limit enforcement, similar to the bracket notation bypass addressed in GHSA-6rw7-vpxm-498p (CVE-2025-15284).\n\n### Details\nWhen the `comma` option is set to `true` (not the default, but configurable in applications), qs allows parsing comma-separated strings as arrays (e.g., `?param=a,b,c` becomes `['a', 'b', 'c']`). However, the limit check for `arrayLimit` (default: 20) and the optional throwOnLimitExceeded occur after the comma-handling logic in `parseArrayValue`, enabling a bypass. This permits creation of arbitrarily large arrays from a single parameter, leading to excessive memory allocation.\n\n**Vulnerable code** (lib/parse.js: lines ~40-50):\n```js\nif (val && typeof val === 'string' && options.comma && val.indexOf(',') > -1) {\n return val.split(',');\n}\n\nif (options.throwOnLimitExceeded && currentArrayLength >= options.arrayLimit) {\n throw new RangeError('Array limit exceeded. Only ' + options.arrayLimit + ' element' + (options.arrayLimit === 1 ? '' : 's') + ' allowed in an array.');\n}\n\nreturn val;\n```\nThe `split(',')` returns the array immediately, skipping the subsequent limit check. Downstream merging via `utils.combine` does not prevent allocation, even if it marks overflows for sparse arrays.This discrepancy allows attackers to send a single parameter with millions of commas (e.g., `?param=,,,,,,,,...`), allocating massive arrays in memory without triggering limits. It bypasses the intent of `arrayLimit`, which is enforced correctly for indexed (`a[0]=`) and bracket (`a[]=`) notations (the latter fixed in v6.14.1 per GHSA-6rw7-vpxm-498p).\n\n### PoC\n**Test 1 - Basic bypass:**\n```\nnpm install qs\n```\n\n```js\nconst qs = require('qs');\n\nconst payload = 'a=' + ','.repeat(25); // 26 elements after split (bypasses arrayLimit: 5)\nconst options = { comma: true, arrayLimit: 5, throwOnLimitExceeded: true };\n\ntry {\n const result = qs.parse(payload, options);\n console.log(result.a.length); // Outputs: 26 (bypass successful)\n} catch (e) {\n console.log('Limit enforced:', e.message); // Not thrown\n}\n```\n**Configuration:**\n- `comma: true`\n- `arrayLimit: 5`\n- `throwOnLimitExceeded: true`\n\nExpected: Throws \"Array limit exceeded\" error.\nActual: Parses successfully, creating an array of length 26.\n\n\n### Impact\nDenial of Service (DoS) via memory exhaustion."}],"impacts":[{"capecId":"CAPEC-130","descriptions":[{"lang":"en","value":"CAPEC-130 Excessive Allocation"}]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":6.3,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"LOW","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]},{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":3.7,"baseSeverity":"LOW","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-20","description":"CWE-20 Improper Input Validation","lang":"en","type":"CWE"}]}],"providerMetadata":{"orgId":"7ffcee3d-2c14-4c3e-b844-86c6a321a158","shortName":"harborist","dateUpdated":"2026-02-12T17:32:05.953Z"},"references":[{"tags":["vendor-advisory"],"url":"https://github.com/ljharb/qs/security/advisories/GHSA-w7fw-mjwx-w883"},{"tags":["patch"],"url":"https://github.com/ljharb/qs/commit/f6a7abff1f13d644db9b05fe4f2c98ada6bf8482"}],"source":{"discovery":"UNKNOWN"},"title":"qs's arrayLimit bypass in comma parsing allows denial of service","x_generator":{"engine":"Vulnogram 0.5.0"}},"adp":[{"references":[{"url":"https://github.com/ljharb/qs/security/advisories/GHSA-w7fw-mjwx-w883","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-02-12T15:00:21.359233Z","id":"CVE-2026-2391","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-02-12T15:00:40.388Z"}}]}}